The invention relates generally to process control, and more particularly to data collection and statistical process control in a manufacturing environment.
Commercially available manufacturing execution system (MES) packages are used throughout semiconductor manufacturing sectors. The statistical process control (SPC) system employed by these commercially available packages, however, frequently operates under incorrect parameters. For example, a typical SPC system operates on an entity and/or lot base, while a typical factory operates on a chamber and/or wafer base. Additionally, these SPC systems are difficult to maintain and require large amounts of statistical process control charts (over 14,000 for a typical fab operation) to achieve effective process monitoring. A statistical process control chart is typically generated by a labor-intensive process.
Particular solutions offered by various vendors for specific applications do not take into account integration arising from different databases and manufacturing systems. Therefore, these solutions cannot adequately address the disadvantages of the described SPC systems. As a result, separate solutions may give rise to communication problems.
Various conventional SPC rules have been developed to assist operators in determining whether machines or processes are not operating properly, or have become “out of control”. The rules are designed to look for patterns in response variables observed from the machine or process. The SPC rules determine if the machine or process is out of control. Generally, these SPC rules are set under the assumption that data are “normally distributed”. These SPC rules are very simple to use, but provide inadequate assistance in managing large quantities of SPC charts.